Regeneration of pancreatic islets in vivo by ultrasound-targeted gene therapy.

ABSTRACT

This study uses a novel approach to gene therapy in which plasmid DNA is targeted to the pancreas in vivo using ultrasound-targeted microbubble destruction (UTMD) to achieve islet regeneration. Intravenous microbubbles carrying plasmids are destroyed within the pancreatic microcirculation by ultrasound, achieving local gene expression that is further targeted to ß-cells by a modified rat insulin promoter (RIP3.1). A series of genes implicated in endocrine development were delivered to rats 2 days after streptozotocin-induced diabetes. The genes, PAX4, Nkx2.2, Nkx6.1, Ngn3 and Mafa, produced α-cell hyperplasia, but no significant improvement in ß-cell mass or blood glucose level 30 days after UTMD. In contrast, RIP3.1-NeuroD1 promoted islet regeneration from surviving ß-cells, with normalization of glucose, insulin and C-peptide levels at 30 days. In a longer-term experiment, four of six rats had a return of diabetes at 90 days, accompanied by ß-cell apoptosis on Tunel staining. Pretreatment with the JNK inhibitor SP600125 successfully blocked ß-cell apoptosis and resulted in restoration of ß-cell mass and normalization of blood glucose level for up to 90 days. This technique allows in vivo islet regeneration, restoration of ß-cell mass and normalization of blood sugar, insulin and C-peptide in rats without viruses.